Abstract: The core system of liquid molten salt reactor is with the characteristics of non-linearity and time-varying. The initial domain of the fuzzy PID control technology cannot change following the change of error, so the control accuracy of the system is deteriorated. Therefore, the core power control strategy based on variable universe fuzzy-PID controller is designed. Taking MSBR core as an example, the simulation results of PID control, fuzzy-PID control and variable universe fuzzy-PID control are compared by using Matlab/Simulink under the disturbance of core inlet temperature or reactivity. The results show that the core power control system based on variable universe fuzzy-PID controller has faster response speed, smaller overshoot and better control effect.